Polymer Having Unsaturated Cycloaliphatic Functionality and Coating Compositions Therefrom

ABSTRACT

A polymer is provided that preferably includes at least one unsaturated cycloaliphatic group. In one embodiment, the polymer is combined with an optional crosslinker and an optional carrier to form a coating composition suitable for use in coating articles such as packaging articles. In one embodiment, the polymer has at least one unsaturated cycloaliphatic group that is at least bicyclic.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/165,679, filed Jan. 28, 2014, entitled “Polymer Having UnsaturatedCycloaliphatic Functionality and Coating Compositions Therefrom,” whichis a continuation of U.S. application Ser. No. 13/833,233, filed Mar.15, 2013, now U.S. Pat. No. 8,663,765, entitled “Polymer HavingUnsaturated Cycloaliphatic Functionality and Coating CompositionsTherefrom,” which is a continuation of U.S. application Ser. No.13/267,928, filed Oct. 7, 2011, now U.S. Pat. No. 8,449,960, entitled“Polymer Having Unsaturated Cycloaliphatic Functionality and CoatingCompositions Formed Therefrom,” which is a continuation-in-partapplication of PCT/US2010/030584 filed on Apr. 9, 2010, entitled“Polymer Having Unsaturated Cycloaliphatic Functionality and CoatingCompositions Formed Therefrom,” which claims priority to U.S.Provisional Application Ser. No. 61/168,138 filed on Apr. 9, 2009,entitled “Polyester Polymer Having Unsaturated CycloaliphaticFunctionality and Coating Composition Formed Therefrom,” each of whichare incorporated herein by reference in their entirety.

TECHNICAL FIELD

This invention relates to a polymer, and coating compositions includingthe polymer.

BACKGROUND

The application of coatings to metals to retard or inhibit corrosion iswell established. This is particularly true in the area of packagingcontainers such as metal food and beverage cans. Coatings are typicallyapplied to the interior of such containers to prevent the contents fromcontacting the metal of the container. Contact between the metal and thepackaged product can lead to corrosion of the metal container, which cancontaminate the packaged product. This is particularly true when thecontents of the container are chemically aggressive in nature.Protective coatings are also applied to the interior of food andbeverage containers to prevent corrosion in the headspace of thecontainer between the fill line of the food product and the containerlid.

Packaging coatings should preferably be capable of high-speedapplication to the substrate and provide the necessary properties whenhardened to perform in this demanding end use. For example, the coatingshould be safe for food-contact, not adversely affect the taste of thepackaged food or beverage product, have excellent adhesion to thesubstrate, resist staining and other coating defects such as “popping”,“blushing” and/or “blistering,” and resist degradation over long periodsof time, even when exposed to harsh environments. In addition, thecoating should generally be capable of maintaining suitable filmintegrity during container fabrication and be capable of withstandingthe processing conditions that the container may be subjected to duringproduct packaging.

Various coatings have been used as interior protective can coatings,including epoxy-based coatings and polyvinyl-chloride-based coatings.Each of these coating types, however, has potential shortcomings. Forexample, the recycling of materials containing polyvinyl chloride orrelated halide-containing vinyl polymers can be problematic. There isalso a desire by some to reduce or eliminate certain epoxy compoundscommonly used to formulate food-contact epoxy coatings.

To address the aforementioned shortcomings, the packaging coatingsindustry has sought coatings based on alternative binder systems such aspolyester resin systems. It has been problematic, however, to formulatepolyester-based coatings that exhibit the required balance of coatingcharacteristics (e.g., flexibility, adhesion, corrosion resistance,stability, resistance to crazing, etc.). For example, there hastypically been a tradeoff between corrosion resistance and fabricationproperties for such coatings. Polyester-based coatings suitable forfood-contact that have exhibited both good fabrication properties and anabsence of crazing having tended to be too soft and exhibit unsuitablecorrosion resistance. Conversely, polyester-based coatings suitable forfood-contact that have exhibited good corrosion resistance havetypically exhibited poor flexibility and unsuitable crazing whenfabricated.

What is needed in the marketplace is an improved binder system for usein coatings such as, for example, packaging coatings.

SUMMARY

In one aspect, the present invention provides a binder system comprisinga polymer having an unsaturated cycloaliphatic group preferablyincluding a double bond, more preferably a carbon-carbon bond, locatedbetween atoms of a ring. The polymer typically includes at least one,and more preferably a plurality, of backbone and/or pendant unsaturatedcycloaliphatic groups. In one embodiment, at least one of theunsaturated cycloaliphatic groups is at least bicyclic (i.e.,polycyclic) and more preferably bicyclic. The polymer may have anysuitable backbone configuration. In preferred embodiments, the backboneincludes at least one heteroatom, with polyester, polyether,polyurethane, and copolymers thereof, being particularly preferredbackbone configurations. In a presently preferred embodiment, thepolymer is a polyester polymer, which may optionally include step-growthlinkages other than ester linkages such as, e.g., urethane linkages,that has a glass transition temperature of preferably at least 0° C.,more preferably at least 20° C. and includes one or more unsaturated atleast bicyclic groups.

In another aspect, the invention provides a coating composition usefulfor coating a wide variety of articles, including metal articles suchas, for example, metal packaging articles. Certain preferred coatingcompositions of the invention are particularly useful for coating metalfood or beverage cans, including use as interior-food-contact coatingsurfaces thereon. The coating composition typically includes a binderpolymer of the invention (preferably in at least a film-forming amount),an optional crosslinker, and an optional carrier. In a presentlypreferred embodiment, the optional crosslinker includes at least onephenolic crosslinker, more preferably at least one resole phenoliccrosslinker. In some embodiments, the polymer of the invention may beself-crosslinking.

In yet another aspect, the invention provides an article coated on atleast a portion of one surface with a coating composition describedherein. In certain embodiments, the coated article comprises a packagingarticle such as a metal food or beverage can, or a portion thereof,having at least a portion of a major surface of a metal substrate (e.g.,a metal substrate of a body portion and/or end portion) coated with acoating composition of the invention.

In yet another aspect, the invention provides a method for producing acoated article. The method includes providing a coating compositiondescribed herein and applying the coating composition on at least aportion of a substrate (typically a planar metal substrate) prior to, orafter, forming the substrate into a packaging article such as a food orbeverage can or a portion thereof.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through lists of examples, which examples can beused in various combinations. In each instance, the recited list servesonly as a representative group and should not be interpreted as anexclusive list.

The details of one or more embodiments of the invention are set forth inthe description below. Other features, objects, and advantages of theinvention will be apparent from the description and from the claims.

SELECTED DEFINITIONS

Unless otherwise specified, the following terms as used herein have themeanings provided below.

The term “aliphatic group” means a saturated or unsaturated linear orbranched hydrocarbon group, which can include optional elements otherthan carbon and hydrogen. This term is used to encompass alkyl, alkenyl,and alkynyl groups, for example. The term “cyclic group” means a closedring hydrocarbon group that is classified as a cycloaliphatic group oran aromatic group, both of which can include heteroatoms. The termcycloaliphatic group means an organic group that contains a ring that isnot an aromatic group.

A group that may be the same or different is referred to as being“independently” something. Substitution is anticipated on the organicgroups of the compounds of the present invention. As a means ofsimplifying the discussion and recitation of certain terminology usedthroughout this application, the terms “group” and “moiety” are used todifferentiate between chemical species that allow for substitution orthat may be substituted and those that do not allow or may not be sosubstituted. Thus, when the term “group” is used to describe a chemicalsubstituent, the described chemical material includes the unsubstitutedgroup and that group with O, N, Si, or S atoms, for example, in thechain (as in an alkoxy group) as well as carbonyl groups or otherconventional substitution. Where the term “moiety” is used to describe achemical compound or substituent, only an unsubstituted chemicalmaterial is intended to be included. For example, the phrase “alkylgroup” is intended to include not only pure open chain saturatedhydrocarbon alkyl substituents, such as methyl, ethyl, propyl, t-butyl,and the like, but also alkyl substituents bearing further substituentsknown in the art, such as hydroxy, alkoxy, alkylsulfonyl, halogen atoms,cyano, nitro, amino, carboxyl, etc. Thus, “alkyl group” includes ethergroups, haloalkyls, nitroalkyls, carboxyalkyls, hydroxyalkyls,sulfoalkyls, etc. On the other hand, the phrase “alkyl moiety” islimited to the inclusion of only pure open chain saturated hydrocarbonalkyl substituents, such as methyl, ethyl, propyl, t-butyl, and thelike. As used herein, the term “group” is intended to be a recitation ofboth the particular moiety, as well as a recitation of the broader classof substituted and unsubstituted structures that includes the moiety.

The term “substantially free” of a particular mobile compound means thatthe compositions of the invention contain less than 100 parts permillion (ppm) of the recited mobile compound. The term “essentiallyfree” of a particular mobile compound means that the compositions of theinvention contain less than 10 ppm of the recited mobile compound. Theterm “essentially completely free” of a particular mobile compound meansthat the compositions of the invention contain less than 1 ppm of therecited mobile compound. The term “completely free” of a particularmobile compound means that the compositions of the invention containless than 20 parts per billion (ppb) of the recited mobile compound.

The term “mobile” means that the compound can be extracted from thecured coating when a coating (typically ˜1 mg/cm² (6.5 mg/in²) thick) isexposed to a test medium for some defined set of conditions, dependingon the end use. An example of these testing conditions is exposure ofthe cured coating to HPLC-grade acetonitrile for 24 hours at 25° C. Ifthe aforementioned phrases are used without the term “mobile” (e.g.,“substantially free of XYZ compound”) then the compositions of thepresent invention contain less than the aforementioned amount of thecompound whether the compound is mobile in the coating or bound to aconstituent of the coating.

The term “crosslinker” refers to a molecule capable of forming acovalent linkage between polymers or between two different regions ofthe same polymer.

The term “on”, when used in the context of a coating applied on asurface or substrate, includes both coatings applied directly orindirectly to the surface or substrate. Thus, for example, a coatingapplied to a primer layer overlying a substrate constitutes a coatingapplied on the substrate.

Unless otherwise indicated, the term “polymer” includes bothhomopolymers and copolymers (i.e., polymers of two or more differentmonomers). Similarly, unless otherwise indicated, the use of a termdesignating a polymer class such as, for example, “polyester” isintended to include both homopolymers and copolymers (e.g.,polyester-urethane polymers).

The term “unsaturation” when used in the context of a compound refers toa compound that includes at least one non-aromatic double bond.

The term “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

The terms “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful, and is not intended to exclude other embodiments from the scopeof the invention.

As used herein, “a,” “an,” “the,” “at least one,” and “one or more” areused interchangeably. Thus, for example, a coating composition thatcomprises “an” additive can be interpreted to mean that the coatingcomposition includes “one or more” additives.

Also herein, the recitations of numerical ranges by endpoints includeall numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, 5, etc.). Furthermore, disclosure of a range includesdisclosure of all subranges included within the broader range (e.g., 1to 5 discloses 1 to 4, 1.5 to 4.5, 1 to 2, etc.).

DETAILED DESCRIPTION

In one aspect, the invention provides a polymer having unsaturatedcycloaliphatic (“UC”) functionality. As used herein, the phrase“unsaturated cycloaliphatic” or “UC” refers to a group that (i) includesone or more unsaturated cycloaliphatic groups and (ii) may include oneor more other groups (e.g., as substituents of the unsaturatedcycloaliphatic group). As such, the term includes both unsaturatedmonocyclic groups and unsaturated polycyclic groups. The polymerpreferably includes at least one, and more preferably a plurality, ofbackbone or pendant UC groups having a double bond located between atomsof a ring, which is preferably a substituted or unsubstitutedhydrocarbon ring that may include one or more heteroatoms in the ring.

Typically, the double bond is a carbon-carbon double bond, althoughother types of double bonds (such as, for example, carbon-oxygen(“C═O”), carbon-nitrogen (“C═N”), nitrogen-nitrogen (“N═N”), andnitrogen-oxygen (N═O) double bonds) may have utility in certainembodiments. In some embodiments, the UC group includes two or moredouble bonds, more typically two or more carbon-carbon double bonds.

In another aspect, the invention is a coating composition that includesthe UC-functional polymer, preferably in a film-forming amount. Whilecoating compositions other than food-contact coating compositions arewithin the scope of this invention, preferred coating compositions ofthe invention are suitable for use as food-contact coatings. It isfurther contemplated that the coating composition of the invention mayhave utility in a variety of other coating end uses, including, otherpackaging coating applications such as, e.g., pharmaceutical or medicalpackaging coating applications; industrial coating applications such as,e.g., appliance coatings; coatings for interior or exterior steelbuilding products; HVAC coating applications; coatings for agriculturalmetal products; wood coatings; etc.

The coating composition of the invention preferably includes aUC-functional polymer, an optional crosslinker (preferably a phenoliccrosslinker), and an optional liquid carrier. The coating compositionpreferably also includes a catalyst (such as, e.g., an acid catalyst) toenhance curing and/or crosslinking Although coating compositionsincluding a liquid carrier are presently preferred, it is contemplatedthat the UC-functional polymer of the invention may have utility inother coating application techniques such as, for example, powdercoating.

The UC-functional polymer of the invention may have any suitablebackbone configuration. Different monomer blocks may be chosen dependingon the intended application, including the desired properties of thefinal product, the expected use of the polymer composition, the othermaterials with which the polymer composition will be mixed or come intocontact, or the type of polymer desired. In presently preferredembodiments, the backbone includes one or more heteroatoms (e.g.,oxygen, nitrogen, silicon, sulfur, phosphorus, etc.), with nitrogen andoxygen being preferred heteroatoms. Step-growth backbones (i.e., polymerbackbones formed through a step-growth polymerization process such as,for example, a condensation polymerization process) are preferredbackbones, with condensation backbones being particularly preferred.Non-limiting examples of suitable backbones including one or moreheteroatoms include polyester, polyether, polyurethane, and copolymerbackbones thereof (e.g., polyester-urethane backbones, polyester-etherbackbones, etc.). Some non-limiting examples of polyester-urethanepolymers are disclosed in International Application No.PCT/US2009/065848 filed on Nov. 25, 2009 and entitled “Polyester Polymerand Coating Compositions Thereof” (Attorney Docket No. 06-1949-0201). Ifdesired, the backbones may include one or more oligomer or polymersegments formed via a chain growth (or addition) polymerization process.

A polyester backbone is particularly preferred. The polyester backbonemay optionally include other step-growth linkages such as, for example,urethane linkages. In some embodiments where a polyester backbone isemployed, the backbone is free of urethane linkages and/or othernon-ester step-growth linkages.

Conventional food-contact, polyester-based packaging coatings havetypically been based on a mixture of a polyester polymer andcrosslinking resin. Such polyesters have typically included relativelyfew reactive hydroxyl groups and, moreover, the reactive groups of thecrosslinking resins have not typically exhibited a high propensity toenter into crosslinking reactions with the hydroxyl groups of thepolyester. Upon curing, relatively few crosslinks are believed to beformed between the polyester and the crosslinking resin, which isthought to result in a network of self-crosslinked crosslinker resinshaving unreacted polyester polymer dispersed therein. Such conventionalpolyester coatings have suffered from a variety of performance issuessuch as poor chemical resistance, a lack of flexibility, and/orunsuitable crazing. (As used herein, the term “crazing” refers tospecific coating defects that occur upon fabrication of a coated metalsubstrate.) While not intending to be bound by any theory, these coatingdefects are believed to be attributable to an increase in thecrystallinity of coating materials that occurs between curing of thecoating and fabrication of the coated article. Unlike conventionalfood-contact polyester coatings, preferred cured coatings of theinvention exhibit a suitable balance of coating properties, includingexcellent corrosion resistance, excellent fabrication properties, and anabsence of crazing.

While not intending to be bound by any theory, the superb balance ofcoating properties exhibited by certain preferred coating compositionsof the invention (including, e.g., where the UC-functional polymer has apolyester backbone) is believed to be attributable, at least in part, toone or more of: (i) the reactivity of the UC groups of the polymer, (ii)the locating of crosslinking sites throughout the polymer (as opposed tomerely at terminal ends as is typical for conventional polyesters)through incorporation of reactive UC groups, (iii) an increased numberof crosslinking sites in the polymer, and/or (iv) the particularselection of crosslinker(s).

As discussed above, in preferred embodiments of the invention, thebinder polymer includes one or more (e.g., ≧2, ≧3, ≧4, ≧5, ≧10, etc.)backbone or pendant UC groups. Non-limiting examples of UC groupsinclude: substituted or unsubstituted unsaturated C3-C13 rings and moretypically substituted or unsubstituted C4-C9 rings (e.g., unsubstitutedor substituted cyclobutenes, cyclopentenes, cyclopentadienes,cyclohexenes, cyclohexadienes, cycloheptenes, cycloheptadienes,cyclooctenes, cyclooctadienes, cyclononenes, cyclodecenes,cyclodecadienes, cycloundecenes, cyclododecenes, cyclotridecenes, andcyclononadienes, and combinations thereof), substituted or unsubstitutedunsaturated polycyclic groups (i.e., at least bicyclic groups, morepreferably bicyclic groups), and combinations thereof. In someembodiments, the aforementioned UC groups may include one or moreheteroatoms (e.g., N, O, S, etc.) in a ring of the UC group. In someembodiments, it may be desirable for the UC group to include one or moreallylic hydrogen attached to a carbon atom of the ring, where the carbonatom is adjacent to a double bond of the ring.

Unsaturated groups that are at least bicyclic (e.g., bicyclic,tricyclic, or higher order polycyclic groups), and more preferablybicyclic, are preferred UC groups. The at least bicyclic groups willtypically include from 5 to 30 carbon atoms, more typically from 6 to 15carbon atoms, and even more typically from 7 to 10 carbon atoms. The atleast bicyclic groups may include one or more heteroatoms (e.g., N, O,S, etc.) in place of one or more of the aforementioned carbon atoms. Theterm “bicyclic” refers to a group that includes two cyclic groups inwhich one or more (and preferably two or more) atoms are present in therings of both of the cyclic groups. Thus, for example, a group thatconsists of two cyclohexane groups connected by a single methlylenelinking group is not a bicyclic group or a polycyclic group.

While not intending to be bound by any theory, the carbon-carbon doublebonds present in unsaturated bicyclic groups such as norbornene arebelieved to exhibit enhanced reactivity. The high level of ring strainpresent in certain unsaturated bicyclic groups (e.g., unsaturated“bridged” bicyclics such as norbornene) is believed to contribute to theenhanced reactivity. For further discussion of the reactivity ofbicyclic compounds, see, for example, D. E. Van Sickel, F. R. Mayo, R.M. Arluck JACS (32)1967, 3680 “Bridging of the cyclohexane ring hasthoroughly deactivated the allylic bridgehead hydrogen atoms andincreased the reactivity of the double bond by 8 to ninefold.” Whilealso not intending to be bound by any theory, it is contemplated thatenhanced reactivity (e.g., between the UC group and a crosslinker) mayalso be achieved using unsaturated ring groups other than bicyclicgroups having appreciable ring strain and, more preferably, a level ofring strain greater than that of a cyclohexene group, and morepreferably approaching or exceeding that of a norbornene group. Whilethe ring strain present in such UC groups may be less than that ofcertain unsaturated bicyclic groups, it may be sufficient for certainend uses. Non-limiting examples of such strained ring groups includesubstituted or unsubstituted variants of the following: cyclopropene(e.g., 1,2-dimethylcyclopropene), cyclobutene, trans-cyclooctene,trans-cyclononene, cyclobutadiene, cyclopentadiene, 1,3-cyclohexadiene,1,3-cycloheptadiene, 1,3-cyclooctadiene, 1,3-cyclononadiene, and1,3-cyclodecadiene, and derivatives and combinations thereof. By way ofexample, a cyclohexene group is not typically considered to be astrained ring group. In the context of monocyclic ring system, ringsincluding 3 to 5 atoms, and especially 3 or 4 atoms, tend to exhibit thegreatest amount of total ring strain. Examples of such strainedmonocylic ring systems are included in the above list.

While not intending to be bound by any theory, in some embodiments,suitable strained ring groups will preferably have at least one doublebond with a heat of hydrogenation greater than that of cyclohexene. Incertain embodiments, the UC group (and preferably a carbon-carbon doublebond of the UC group) has a heat of hydrogenation that is at least aboutas high as that of bicyclo[2.2.2]octene (e.g., −28.25 kcal/mole), andmore preferably, at least about as high as that of bicyclo[2.2.1]heptene(e.g., −33.13 kcal/mole). As used herein, when a heat of hydrogenationis stated to be, for example, “at least X,” “greater than X,” or thelike, it should be understood that reference is made to the absolutevalue of the heat of hydrogenation because heats of hydrogenation aretypically reported as negative values, with a larger negative valueindicating a higher heat of hydrogenation (e.g., −40 kcal/mole is ahigher heat of hydrogenation than −10 kcal/mole). It is alsocontemplated that certain reactive aliphatic (or open chain)carbon-carbon double bonds may be substituted for some, or all, of theUC groups of the polymer. Suitable such groups may include carbon-carbondouble bonds having, for example, a heat of hydrogenation that is (i)greater than that of cyclohexene or (ii) at least about as high as thatof bicyclo[2.2.2]octene. Preferred reactive aliphatic carbon-carbondouble bonds are capable of reacting under coating cure conditionsdescribed herein with a suitable crosslinker, such as for, example aresole phenolic crosslinker, to form a covalent linkage between thepolymer and the crosslinker.

In one embodiment, the UC group includes a bicyclic structurerepresented by the IUPAC (International Union of Pure and AppliedChemistry) nomenclature Expression (I):

bicyclo[x.y.z]alkene

In Expression (I),

-   -   x is an integer having a value of 2 or more,    -   y is an integer having a value of 1 or more,    -   z is an integer having a value of 0 or more, and    -   the term alkene refers to the IUPAC nomenclature designation        (e.g., hexene, heptene, heptadiene, octene, etc.) for a given        bicyclic molecule and denotes that the bicyclic group includes        one or more double bonds (e.g. ≧1, ≧2, ≧3 double bonds).

Preferably z in Expression (I) is 1 or more. In other words, preferredbicyclic groups include a bridge with a least one atom (typically one ormore carbon atoms) interposed between a pair of bridgehead atoms, wherethe at least one atom is shared by at least two rings. By way ofexample, bicyclo[4.4.0]decane does not include such a bridge.

In preferred embodiments, x has a value of 2 or 3 (more preferably 2)and each of y and z independently have a value of 1 or 2.

Non-limiting examples of some suitable UC groups represented byExpression (I) include monovalent or polyvalent (e.g., divalent)variants of bicyclo[2.1.1]hexene, bicyclo[2.2.1]heptene (i.e.,norbornene), bicyclo[2.2.2]octene, bicyclo[2.2.1]heptadiene, andbicyclo[2.2.2]octadiene. Bicyclo[2.2.1]heptene is a presently preferredUC group.

It is contemplated that the UC groups represented by Expression (I) maycontain one or more heteroatoms (e.g., nitrogen, oxygen, sulfur, etc.)and may be substituted to contain one or more additional substituents.For example, one or more cyclic groups (including, e.g., pendant cyclicgroups and ring groups fused to a ring of a bicyclic UC group) oracyclic groups may be attached to the bicyclic group represented byExpression (I). Thus, for example, in some embodiments the bicyclicgroup of Expression (I) may be present in a tricyclic or higher group.

If desired, UC-functional polymers of the invention may includenon-cycloaliphatic unsaturation. For example, certain UC-functionalpolymers may include aliphatic unsaturation (i.e., open chain or linearunsaturation) and/or aromatic unsaturation.

Iodine value is a useful measure for characterizing the average numberof non-aromatic double bonds present in a material. UC-functionalpolymers of the invention may have any suitable iodine value to achievethe desired result. In preferred embodiments, the UC-functional polymershave an iodine value of at least about 10, more preferably at leastabout 20, even more preferably at least about 35, and optimally at leastabout 50. The upper range of suitable iodine values is not limited, butin most embodiments the iodine value typically will not exceed about120. Iodine values are typically expressed in terms of centigrams ofiodine per gram of resin and may be determined, for example, using themethodology provided in the below Test Methods section.

In some embodiments, the UC-functional polymer includes a number of UCgroups, and more preferably a number of unsaturated at least bicyclicgroups (more preferably bicyclic), sufficient to yield an iodine valueof at least 5, at least 10, at least 20, at least 35, or at least 50(before factoring in the portion of the total iodine value of thepolymer attributable to any other carbon-carbon double bonds that may bepresent in the polymer).

The UC-functional polymer of the invention may include any suitablenumber of UC groups. As discussed above, one useful measure of suchgroups is the number of such groups present in the polymer. Anotheruseful measure is the weight percent of the UC groups relative to thetotal weight of the polymer. In certain preferred embodiments, the UCgroups constitute at least about 5, more preferably at least about 15,and even more preferably at least about 30 weight percent (“wt-%”) ofthe polymer. Preferably, the UC groups constitute less than about 95,more preferably less than about 75, and even more preferably less thanabout 50 wt-% of the polymer. In some embodiments, such as, for example,when open-chain unsaturation is incorporated into the polymer (e.g.,using materials such as maleic acid or anhydride), an amount of UCgroups less than that recited above may be used. In certain preferredembodiments, the UC-functional polymer includes a number of at leastbicyclic groups, more preferably bicyclic groups, sufficient to yield awt-% of at least bicyclic groups pursuant to that described above.

Caution should be exercised when interpreting the wt-% of UC groupsbecause direct measurement of the weight of the UC groups may not befeasible. Accordingly, the aforementioned wt-%'s correspond to the totalweight of (a) UC-containing monomers relative to (b) the total weight ofthe UC-functional polymer. Thus, for example, if an oligomer having a UCgroup is incorporated into the backbone of the polymer, the wt-% of UCgroup in the polymer is calculated using the weight of the monomer thatincludes the UC group (as opposed to the weight of the oligomer thatincludes the monomer). Similarly, if the polymer is formed and then amonomer of the preformed polymer is modified to include the UC group,then the wt-% of UC groups in the polymer is calculated using the weightof the modified monomer, which may be based on a theoretical calculationif necessary. For example, in some embodiments, bicyclic UC groups maybe incorporated into the polymer via a Diels-Alder reaction of aconjugated diene component (e.g., cyclopentadiene and/ordicyclopentadiene) across a double bond of a monomer present in thebackbone of the polymer (e.g., maleic acid and/or anhydride reacted intothe polymer backbone). In this situation, the wt-% of UC groups in thepolymer is determined using the weight of the resultingbicyclic-modified monomer present in the polymer (e.g., the weight ofcyclopentadienized maleic anhydride).

In certain preferred embodiments, the UC group is connected to at leastone other portion of the polymer via a step-growth linkage (e.g., acondensation linkage) such as, for example, an amide, carbamate,carbonate ester (—O—C(═O)—O—), ester, ether, urea, or urethane linkagegroup. A covalent linkage formed from, for example, an additionpolymerization reaction (e.g., a free-radical-initiated additionpolymerization such as a vinyl polymerization) is not considered astep-growth linkage. Ester linkages are presently preferred step-growthlinkages. If desired, other organic linkage groups such as, for example,substituted or unsubstituted hydrocarbyl linking groups may also beused.

As previously discussed, in some preferred embodiments, theUC-functional polymer has a polyester backbone. In one such embodiment,the UC-functional polyester polymer includes at least one divalentbackbone UC group that is connected on each end to another portion ofthe backbone via a step-growth linkage, more preferably an esterlinkage.

In some embodiments, the binder polymer includes one or more divalentbackbone segments having the structure —X—Z—X—, where: (i) each X isindependently a step-growth linkage, and typically both X are the sametype of step-growth linkage and (ii) Z is a divalent organic group thatincludes at least one unsaturated at least bicyclic group. In presentlypreferred embodiments, Z includes two or more carbon atoms in a chainconnecting the two X groups, more preferably from 2 to 8, 2 to 6, or 2to 4 such carbon atoms. In an embodiment, each X is an ester grouporiented such that the —X—Z—X— segment has the structure—O—C(O)—Z—C(O)—O—.

In a presently preferred embodiment, Z includes two carbons atoms in thechain connecting the two X groups. An example of a preferred divalent—X—Z—X— group having two such carbon atoms is depicted below:

Suitable polyester polymers may be prepared using standard condensationreactions. The polyester polymer is typically derived from a mixture ofat least one polyfunctional alcohol (“polyol”) esterified with at leastone polycarboxylic acid (or derivative thereof). In some embodiments, atransesterification polymerization or other process may be used. Ifdesired, the polyester polymer may include polymer linkages (e.g.,amide, carbamate, carbonate ester, ether, urea, urethane, etc.), sidechains, and end groups not related to simple polyol and polyacidcomponents.

Non-limiting examples of suitable polycarboxylic acids includedicarboxylic acids and polycarboxylic acids having higher acidfunctionality (e.g., tricarboxylic acids, tetracarboxylic acids, etc.)or anhydrides thereof, precursors or derivatives thereof (e.g., anesterifiable derivative of a polycarboxylic acid, such as a dimethylester or anhydride), or mixtures thereof. Suitable polycarboxylic acidsmay include, for example, maleic acid, fumaric acid, succinic acid,adipic acid, phthalic acid, tetrahydrophthalic acid,methyltetrahydrophthalic acid, hexahydrophthalic acid,methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid,azelaic acid, sebacic acid, isophthalic acid, trimellitic acid,terephthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, glutaric acid, dimer fatty acids, anhydrides orderivatives thereof, and mixtures thereof. If desired, adducts ofpolyacid compounds (e.g., triacids, tetraacids, etc.) and monofunctionalcompounds may be used. An example of one such adduct is pyromelliticanhydride pre-reacted with benzyl alcohol. It should be understood thatin synthesizing the polyester, the specified acids may be in the form ofanhydrides, esters (e.g., alkyl ester) or like equivalent form. For sakeof brevity, such compounds are referred to herein as “carboxylic acids.”

Non-limiting examples of suitable polyols include diols, polyols having3 or more hydroxyl groups (e.g., triols, tetraols, etc.), andcombinations thereof. Suitable polyols may include, for example,ethylene glycol, propylene glycol, 1,3-propanediol, glycerol, diethyleneglycol, dipropylene glycol, triethylene glycol, trimethylolpropane,trimethylolethane, tripropylene glycol, neopentyl glycol,pentaerythritol, 1,4-butanediol, hexylene glycol, cyclohexanedimethanol,a polyethylene or polypropylene glycol, isopropylidenebis(p-phenylene-oxypropanol-2), and mixtures thereof. If desired,adducts of polyol compounds (e.g., triols, tetraols, etc.) andmonofunctional compounds may be used. An example of one such adduct isdipentaerythritol pre-reacted with benzoic acid.

In some embodiments, the backbone of the polyester polymer ishydroxyl-terminated and/or carboxyl-terminated, more preferablyhydroxyl-terminated.

The polyester polymer may include polymer segments other than polyestersegments. Typically, however, at least 50 wt-% of the polyester willcomprise polyester segments. In some embodiments, substantially all(e.g., >80 wt-%, >90 wt-%, >95 wt-%, etc.), or all, of the polyestercomprises polyester segments.

The polyester polymer may have any suitable hydroxyl number. Hydroxylnumbers are typically expressed as milligrams of potassium hydroxide(KOH) equivalent to the hydroxyl content of 1 gram of thehydroxyl-containing substance. Methods for determining hydroxyl numbersare well known in the art. See, for example, ASTM D1957-86 (Reapproved2001) entitled “Standard Test Method for Hydroxyl Value of Fatty Oilsand Acids” and available from the American Society for Testing andMaterials International of West Conshohocken, Pa. In certain preferredembodiments, the polyester polymer has a hydroxyl number of from 0 toabout 150, even more preferably from about 5 to about 100, and optimallyfrom about 10 to about 80.

The polyester polymer may have any suitable acid number. Acid numbersare typically expressed as milligrams of KOH required to titrate a1-gram sample to a specified end point. Methods for determining acidnumbers are well known in the art. See, for example, ASTM D974-04entitled “Standard Test Method for Acid and Base Number byColor-Indicator Titration” and available from the American Society forTesting and Materials International of West Conshohocken, Pa. The rangeof suitable acid numbers may vary depending on a variety ofconsiderations including, for example, whether water-dispersibility isdesired. In some embodiments, the polyester polymer has an acid numberof at least about 5, more preferably at least about 15, and even morepreferably at least about 30. Depending on the desired monomerselection, in certain embodiments (e.g., where a solvent-based coatingcomposition is desired), the polyester polymer has an acid number ofless than about 40, less than about 10, or less than about 5.

In some embodiments, the polymer includes one or more urethane linkages,and more preferably a plurality of urethane linkages (e.g., ≧2, ≧3, ≧4,≧5, ≧10, etc.). Thus, for example, in some such embodiments, the polymeris a polyester-urethane polymer. Urethane linkages are typically formedby reacting ingredients that include one or more hydroxyl-functionalcompounds and one or more isocyanate-functional compounds. If desired, apolyester-urethane polymer may be formed, for example, through reactionof a polyester polyol and a diisocyanate or other polyisocyanatecompound.

The isocyanate compound may be any suitable compound, including anisocyanate compound having 1 isocyanate group; a polyisocyanate compoundhaving 2, 3, or 4 or more isocyanate groups; or a mixture thereof.Suitable diisocyanates may include isophorone diisocyanate (i.e.,5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane);5-isocyanato-1-(2-isocyanatoeth-1-yl)-1,3,3-trimethylcyclohexane;5-isocyanato-1-(3-isocyanatoprop-1-yl)-1,3,3-trimethylcyclohexane;5-isocyanato-(4-isocyanatobut-1-yl)-1,3,3-trimethylcyclohexane;1-isocyanato-2-(3-isocyanatoprop-1-yl)cyclohexane;1-isocyanato-2-(3-isocyanatoeth-1-yl)cyclohexane;1-isocyanato-2-(4-isocy-anatobut-1-yl)cyclohexane;1,2-diisocyanatocyclobutane; 1,3-diisocyanatocyclobutane;1,2-diisocyanatocyclopentane; 1,3-diisocyanatocyclopentane;1,2-diisocyanatocyclohexane; 1,3-diisocyanatocyclohexane;1,4-diisocyanatocyclohexane; dicyclohexylmethane 2,4′-diisocyanate;trimethylene diisocyanate; tetramethylene diisocyanate; pentamethylenediisocyanate; hexamethylene diisocyanate; ethylethylene diisocyanate;trimethylhexane diisocyanate; heptamethylene diisocyanate;2-heptyl-3,4-bis(9-isocyanatononyl)-1-pentyl-cyclohexane; 1,2-, 1,4-,and 1,3-bis(isocyanatomethyl)cyclohexane; 1,2-, 1,4-, and1,3-bis(2-isocyanatoeth-1-yl)cyclohexane;1,3-bis(3-isocyanatoprop-1-yl)cyclohexane; 1,2-, 1,4- or1,3-bis(4-isocyanatobuty-1-yl)cyclohexane; liquidbis(4-isocyanatocyclohexyl)-methane; and derivatives or mixturesthereof.

In some embodiments, the isocyanate compounds are preferablynon-aromatic. Non-aromatic isocyanates are particularly desirable forcoating compositions intended for use on an interior surface of a foodor beverage container. Isophorone diisocyanate (IPDI) and hexamethylenediisocyanate (HMDI) are preferred non-aromatic isocyanates.

If water-dispersibility is desired, the UC-functional polymer can bemade water-dispersible using any suitable means, including the use ofnon-ionic water-dispersing groups, salt groups (e.g., anionic and/orcationic salt groups), surfactants, or a combination thereof. Preferredwater-dispersible UC-functional polymers contain a suitable amount ofsalt-containing (e.g., anionic and/or cationic salt groups) and/orsalt-forming groups to facilitate preparation of an aqueous dispersionor solution. Suitable salt-forming groups may include neutralizablegroups such as acidic or basic groups. At least a portion of thesalt-forming groups may be neutralized to form salt groups useful fordispersing the polymer into an aqueous carrier. Acidic or basicsalt-forming groups may be introduced into the polymer by any suitablemethod.

Non-limiting examples of anionic salt groups include neutralized acid oranhydride groups, sulphate groups (—OSO₃ ⁻), phosphate groups (—OPO₃ ⁻),sulfonate groups (—SO₂O⁻), phosphinate groups (—POO⁻), phosphonategroups (—PO₃ ⁻), and combinations thereof. Non-limiting examples ofsuitable cationic salt groups include:

(referred to, respectively, as quaternary ammonium groups, quaternaryphosphonium groups, and tertiary sulfate groups) and combinationsthereof. Non-limiting examples of non-ionic water-dispersing groupsinclude hydrophilic groups such as ethylene oxide groups. Compounds forintroducing the aforementioned groups into polymers are known in theart.

In some embodiments, a water-dispersible UC-functional polymer may beachieved through inclusion of a sufficient number of carboxylic acidgroups in the polymer. Non-limiting examples of suitable materials forincorporating such groups into the polymer include anhydrides orpolyanhydrides such as tetrahydrophthalic anhydride, pyromelliticanhydride, pyromellitic dianhydride, succinic anhydride, trimilleticanhydride (“TMA”), and mixtures thereof. In one embodiment, ahydroxyl-terminated polyester polymer or oligomer having one or morependant hydroxyl groups is reacted with an anhydride such as TMA toproduce a hydroxyl-terminated polyester having carboxylic functionality.The conditions of the reaction are preferably controlled, including thetemperature, to avoid gelling. The resulting carboxylic-functionalpolyester oligomer or polymer is neutralized (e.g., using a base such asan amine) to produce an aqueous dispersion. In some embodiments, it iscontemplated that water-dispersibility may be provided through use ofacid-functional ethylenically unsaturated monomers that have beengrafted onto the polymer, whereby a suitable number of theacid-functional groups are neutralized with base (such as, e.g., atertiary amine) to produce salt groups. See for example, U.S. Pat. App.No. 20050196629 for examples of such techniques.

The molecular weight of the UC-functional polymer of the invention canvary depending upon material choice and the desired end use. Inpreferred embodiments, the polymer has a number average molecular weight(Mn) of at least about 1,000, more preferably at least about 1,500, andeven more preferably at least about 3,000. Preferably, the Mn of thepolymer is less than about 20,000, more preferably less than about15,000, and even more preferably less than about 10,000.

The desired glass transition temperature (Tg) may vary depending upon avariety of factors, including, for example, the structure of theUC-functional polymer, the desired molecular weight of the UC-functionalpolymer and the desired end use. In embodiments where the UC-functionalpolymer is a polyester polymer and the coating composition is intendedfor use an interior food-contact coating of a packaging article, theUC-functional polymer preferably has a Tg that is sufficiently high suchthat the cured film exhibits good corrosion resistance. SuchUC-functional polyester polymers preferably have a Tg of at least 0° C.,more preferably at least 15° C., even more preferably at least 20 or 25°C. Although the Tg is not especially limited on the upper end, suchUC-functional polyester polymers typically have a Tg of less than about170° C., more typically less than about 150° C., and even more typicallyless than about 130° C.

Preferred UC-functional polymers of the present invention include aplurality of aromatic groups, with aromatic polyesters beingparticularly preferred. Preferred aromatic UC-functional polymersinclude at least about 5 wt-%, more preferably at least about 10 wt-%,even more preferably at least about 15 wt-%, and even more preferably atleast about 20 wt-% of aromatic groups. In some embodiments, theUC-functional polymer may include up to 75 wt-% or more of aromaticgroups. The aforementioned wt-%'s correspond to the total weight ofaromatic monomers used to form the UC-functional polymer relative to thetotal weight of the reactants used to form polymer. Thus, for example,if an oligomer having an aromatic group is incorporated into theUC-functional polymer, the wt-% of the aromatic group in the polymer iscalculated using the weight of the aromatic monomer used to form theoligomer (as opposed to the weight of the oligomer). Suitable aromaticmonomers include, for example, acid-, ester-, or anhydride-functionalaromatic monomers (e.g., aromatic monoacids and/or polyacids, morepreferably aromatic polyacids); hydroxyl-functional aromatic monomers(e.g., aromatic mono- and/or poly-functional monomers); or aromaticmonomers having one or more (typically at least two) reactive groupscapable of participating in a condensation reaction with a complimentaryreactive group (more preferably, a hydroxyl, carboxylic acid, ester, oranhydride groups) to form a covalent linkage. Examples of suitablearomatic monomers include terephthalic acid, isophthalic acid, phthalicacid, phthalic anhydride, trimellitic anhydride, trimellitic acid,dimethyl terephthalate, dimethyl isophthalate, dimethyl phthalate,5-sodiosulpho isophthalic acid, naphthalic acid, 1,8-naphthalicanhydride, dimethyl naphthalate, pyromellitic dianhydride, andderivatives and combinations thereof.

In some embodiments, the UC-functional polymer of the present inventionis preferably free or appreciably free of fatty acids, oils, and/orother long-chain hydrocarbons. It is believed that the use of unsuitableamounts of such materials may impart undesirable off-tastes or odors topackaged food or beverage products that are kept in prolonged contactwith the coating compositions of the present invention. In addition, thepresence of unsuitable amounts of such materials in the UC-functionalpolymer may cause the corrosion resistance of coating compositions ofthe present invention to be unsuitable for certain end uses, especiallyfor packaging coatings intended for use with so called “hard-to-hold”food or beverage products. In presently preferred embodiments, theUC-functional polymer of the present invention includes no more than 10wt-%, more preferably no more than 3 wt-%, and even more preferably nomore than 1 wt-% of fatty acids, oils, or other long-chain hydrocarbons(e.g., having 8 or more carbon atoms such as, e.g., ≧C10, ≧C12, ≧C15,≧C20, ≧C30), based on the total non-volatile weight of the ingredientsused to make the UC-functional polymer.

It is contemplated that in certain embodiments, the UC-functionalpolymer may include some long-chain hydrocarbons having 12 or lesscarbon atoms such as, for examples, sebacic acid.

Similarly, presently preferred coating compositions of the invention arepreferably free or appreciably free of fatty acids and oils. Preferredcoating compositions include no more than 20 wt-%, more preferably nomore than 10 wt-%, and even more preferably no more than 5 wt-% of oilsand fatty acids, based on the total nonvolatile weight of the coatingcomposition.

In presently preferred embodiments, the UC-functional polymer is not analkyd resin.

Coating compositions of the invention may include any suitable amount ofUC-functional polymer to produce the desired result. In preferredembodiments, the coating composition includes from about 50 to about 100wt-% of UC-functional polymer, more preferably at least about 60 wt-% ofUC-functional polymer, and even more preferably at least about 70 wt-%of UC-functional polymer, based on the total nonvolatile weight of thecoating composition. Preferably, the coating compositions include lessthan about 99, more preferably less than about 95, and even morepreferably less than about 80 wt-% of UC-functional polymer, based onthe total nonvolatile weight of the coating composition.

Preferred UC-functional polymers and/or coating compositions of theinvention are preferably substantially free, more preferably essentiallyfree, even more preferably essentially completely free, and optimallycompletely free of mobile bisphenol A (BPA) and aromatic glycidyl ethercompounds (e.g., diglycidyl ethers of bisphenol (BADGE), diglycidylethers of bisphenol F (BFDGE), and epoxy novalacs). In certain preferredembodiments, the UC-functional polymer and/or coating composition of theinventions are preferably substantially free, more preferablyessentially free, even more preferably essentially completely free, andoptimally completely free of bound BPA and aromatic glycidyl ethercompounds (e.g., BADGE, BFDGE and epoxy novalacs).

In some embodiments, the UC-functional polymer and/or coatingcomposition is at least substantially “epoxy-free,” more preferably“epoxy-free.” The term “epoxy-free,” when used herein in the context ofa polymer, refers to a polymer that does not include any “epoxy backbonesegments” (i.e., segments formed from reaction of an epoxy group and agroup reactive with an epoxy group). Thus, for example, a polymer madefrom ingredients including an epoxy resin would not be consideredepoxy-free. Similarly, a polymer having backbone segments that are thereaction product of a bisphenol (e.g., bisphenol A, bisphenol F,bisphenol S, 4,4′dihydroxy bisphenol, etc.) and a halohdyrin (e.g.,epichlorohydrin) would not be considered epoxy-free. However, a vinylpolymer formed from vinyl monomers and/or oligomers that include anepoxy moiety (e.g., glycidyl methacrylate) would be consideredepoxy-free because the vinyl polymer would be free of epoxy backbonesegments. The coating composition of the invention is also preferably atleast substantially epoxy-free, more preferably epoxy-free.

In some embodiments, the UC-functional polymer is “PVC-free,” andpreferably the coating composition is also “PVC-free.” That is, eachcomposition preferably contains less than 2 wt-% of vinyl chloridematerials, more preferably less than 0.5 wt-% of vinyl chloridematerials, and even more preferably less than 1 ppm of vinyl chloridematerials.

UC functionality may be incorporated into the polymer of the inventionusing any suitable means. For example, the functionality may be providedby either of the following non-limiting approaches: (A) forming apolymer from a mixture of reactants including one or more reactantshaving a UC group or (B) modifying a preformed oligomer or polymer toinclude a UC group.

Non-limiting examples of reactants having a UC group includeUC-functional reactants having one or more active hydrogen groups suchas, for example, acids or anhydrides (e.g., nadic acid or anhydride,methyl-nadic acid or anhydride, tetrahydrophthalic acid or anhydride,methyltetrahydrophthalic acid or anhydride, derivatives thereof, andmixtures thereof). UC-functional anhydrides are presently preferred,with anhydrides having an unsaturated bicyclic group being particularlypreferred. Non-limiting examples of other suitable active hydrogengroups include groups having a hydrogen attached to an oxygen (O),sulfur (S), and/or nitrogen (N) atom as in the groups —OH, —COOH, —SH,═NH, and NH₂.

A non-limiting example of the above approach (B) includes the steps of:

-   -   1. providing a polymer (e.g., a polyester polymer) having        reactive functional groups capable of participating in a        step-growth reaction such as, for example, carboxylic, hydroxyl,        amine, carbonate ester, isocyanate groups, or mixtures thereof;    -   2. providing a compound having (i) a UC group and (ii) a        functional group capable of reacting with the aforementioned        functional group of the polymer to form a step-growth linkage        such as, for example, an ester, amide, urethane, urea, urethane,        or carbonate ester linkage; and    -   3. reacting the polymer and the aforementioned compound to form        a polymer including a UC group.

Another non-limiting example of approach (B) above includes providing apreformed unsaturated oligomer or polymer and using a Diels-Alderreaction to modify the oligomer or polymer (e.g., using cyclopentadieneor dicyclopentadiene, or a derivative thereof as the conjugated dienecomponent) to include an unsaturated bicyclic group. Materials andmethods for producing a bicyclic Diels-Alder reaction product arediscussed in WO 2008/124682. Non-limiting examples of other usefulDiels-Alder reactants (e.g., as the conjugated diene component) mayinclude anthracene, cyclohexadiene, cyclopentadiene (including, e.g.,1-alkyl cyclopentadienes or 2-alkyl cyclopentadienes), furan, thiophene,and combinations or derivatives thereof.

Maleic anhydride and maleic acid are examples of preferred compounds forincorporating unsaturation into an oligomer or polymer for purposes ofparticipating in a Diels-Alder reaction (e.g., with a conjugated dienecomponent such as cyclopentadiene, dicyclopentadiene, and/or a variantor derivative thereof) to provide an unsaturated at least bicyclicgroup. While not intending to be bound by any theory, it is believedthat maleic acid and maleic anhydride are particularly strongdienophiles, which allows the Diels-Alder reaction to be conducted at alower temperature (e.g., from about 150 to about 200° C. as opposed to,e.g., from 260 to 280° C. as may be required for unsaturated fatty acidsor oils), which may be beneficial in certain embodiments. In someembodiments, it is preferred that 1 mole or less of the conjugated dienecomponent (e.g., cyclopentadiene), or 0.5 moles or less in the case ofdicyclopentadiene, be used per 1 mole of unsaturated monomer blockspresent in the oligomer or polymer.

In some embodiments, the coating composition of the present inventionprior to cure (e.g., the liquid coating composition), includes less than1,000 parts-per-million (“ppm”), preferably less than 200 ppm, and morepreferably less than 100 ppm of low-molecular weight (e.g., <500 g/mol,<200 g/mol, <100 g/mol, etc.) ethylenically unsaturated compounds.Examples of such low-molecular weight ethyenically unsaturated compoundsinclude any of the low-molecular weight conjugated diene componentsreferenced herein such as, for example, anthracene, cyclohexadiene,cyclopentadiene, dicyclopentadiene, furan, thiophene, or a derivativethereof.

In some embodiments, it may be advantageous to provide a polymer polyolsuch as, for example, a polyester polyol having an Mn from about 500 toabout 5,000 and react the polymer polyol with a dianhydride to upgradethe molecular weight. In certain embodiments, the mole ratio of polymerpolyol (e.g., polyester polyol) to dianhydride is from about 5:1 toabout 50:1, and more preferably from about 15:1 to about 25:1. Thereaction is preferably controlled to avoid gelling. For example, thereaction temperature is preferably maintained at a temperature of lessthan about 150° C. (more preferably from about 90° C. to about 120° C.)to avoid gelling. Non-limiting examples of suitable dianhydrides includepyromellitic dianhydride, naphthalene tetracarboxylic dianhydride,benzophenone tetracarboxylic dianhydride, biphenyl tetracarboxylicdianhydride, butane tetracarboxylic dianhydride, cyclobutanetetracarboxylic dianhydride, cyclopentane tetracarboxylic dianhydride,and combinations thereof. In certain embodiments, the UC-functionalpolymer of the invention includes one or more dianhydrides in an amountfrom about 0.5 to about 70 wt-%, more preferably from about 2 to about40 wt-%, and even more preferably from about 3 to about 10 wt-%, basedon the total nonvolatile weight of reactants.

In some polyester-based embodiments, the coating composition of theinvention can include one or more saturated or unsaturated polyesterpolymers in addition to a UC-functional polyester polymer of theinvention. In some such embodiments, at least a majority (e.g., >50wt-%, >60 wt-%, >75 wt-%, >90 wt-%, etc.), and more preferably all, orsubstantially all, of the total amount of polyester polymers included inthe coating composition are UC-functional polyester polymers.

In some embodiments, the coating composition of the invention is free orsubstantially free (e.g., contains less than about 1 wt-%, based onsolids) of one or both of acrylic resins or acrylated polyester resins.

When present, the concentration of one or more optional crosslinkers inthe coating composition may vary depending upon the desired result. Forexample, in some embodiments, the coating composition may contain fromabout 0.01 to about 50 wt-%, more preferably from about 5 to about 50wt-%, even more preferably from about 10 to about 40 wt-%, and optimallyfrom about 15 to about 30 wt-% of one or more crosslinkers, by weight ofnonvolatile material in the coating composition.

Any suitable crosslinker or combination of crosslinkers can be used. Forexample, phenolic crosslinkers (e.g., phenoplasts), amino crosslinkers(e.g., aminoplasts), blocked isocyanate crosslinkers, epoxy-functionalcrosslinkers, and combinations thereof, may be used. Preferredcrosslinkers are at least substantially free, more preferably completelyfree, of bound BPA and aromatic glycidyl ethers.

Examples of suitable phenolic crosslinkers include the reaction productsof aldehydes with phenols. Formaldehyde and acetaldehyde are preferredaldehydes. Non-limiting examples of suitable phenols that can beemployed include phenol, cresol, p-phenylphenol, p-tert-butylphenol,p-tert-amylphenol, cyclopentylphenol, cresylic acid, BPA (not presentlypreferred), and combinations thereof.

Resole-type phenolic crosslinkers are presently preferred for certainfood or beverage coating applications and, in particular, forfood-contact coatings. While not intending to be bound by any theory,cured packaging coatings formulated using a UC-functional polymer of theinvention and one or more resole-type phenolic crosslinkers (with orwithout additional crosslinkers such as, e.g., non-resole phenoliccrosslinkers, amino crosslinkers, and/or blocked isocyanate) have beenobserved to exhibit superior coating properties relative to comparablecured packaging coatings formulated without resole-type phenoliccrosslinkers. In preferred embodiments, upon curing of the coating, theresole-type phenolic crosslinker is believed to form a covalent bondwith a UC group of the UC-functional polymer, resulting in the formationof a crosslinked polymer network including both the phenolic crosslinkerand the UC-functional polymer. While not intending to be bound by anytheory, this is believed to be responsible, at least in part, for theenhanced coating properties exhibited by certain preferred packagingcoatings of the invention relative to certain conventional packagingcoatings containing, for example, polyester and phenolic resins that donot form, or do not appreciably form, such a polymer network with eachother.

Some preferred embodiments of the coating composition of the inventioninclude (i) a UC-functional polymer, more preferably a UC-functionalpolyester polymer having unsaturated at least bicyclic groups (morepreferably bicyclic UC groups) and (ii) at least one crosslinker in theform of a resole phenolic crosslinker. While not intending to be boundby any theory, the UC group and the resole phenolic crosslinker arebelieved to react with one another during coating cure to form acovalent linkage between the UC-functional polymer and the resolephenolic crosslinker.

While not intending to be bound by any theory, a simplified Diagram (I)is provided below depicting the reaction that is believed to occurbetween the UC group and a resole phenolic under suitable reactionconditions.

In the above Diagram (I), the dotted lines are included to illustratethe proposed reaction mechanism; R and R′ depict other structuralportions of the phenolic crosslinker; and a backbone bicyclic UC group(and more specifically a backbone norbornyl group) is included as anillustrative UC group. As shown in Diagram (I), two covalent attachmentsare believed to be formed and are believed to be present in a so called“Chroman Ring”, which includes the aromatic ring of the phenoliccrosslinker and the ring that is believed to be formed between thephenolic aromatic group and the UC group. Thus, in some embodiments, itis believed that two covalent linkages are formed between the UC groupand the phenolic crosslinker with one being an ether linkage group andthe other a hydrocarbyl linkage group (e.g., a divalent methylenegroup). The Chroman Ring attaching group is believed to result inenhanced coating properties. In addition to bicyclic UC groups, it isbelieved that a Chroman Ring can also be formed when using monocyclic UCgroups and/or tricyclic or higher polycyclic UC groups. It is alsocontemplated that certain open chain carbon-carbon double bonds may becapable of participating in a similar reaction with resole phenoliccrosslinker to form covalent linkages between the binder polymer and thephenolic crosslinker.

Non-limiting examples of suitable resole phenolic crosslinkers includethe DUREZ 33160 and 33162 products (each available from DurezCorporation, Addison, Tex.), the BAKELITE 6535 and 6470 products (eachavailable from Hexion Specialty Chemicals GmbH), the PHENODUR PR 285 andPR 812 products (each available from CYTEC Surface Specialties, Smyrna,Ga.), and the SFC 112 and 142 products (each available from the SIGroup, previously Schenectady), and mixtures thereof. In someembodiments, the coating composition includes, on a total solids basis,at least about 5, more preferably at least about 10, and even morepreferably at least about 15 wt-% of phenolic crosslinker. Preferably,some or all of the phenolic crosslinker is resole phenolic crosslinker.A resole phenolic typically includes at least one methylol group or atleast one group derived from a methylol group such as, for example, abutylated methyol group. In contrast, a novolac phenolic does notinclude a methylol group or a group derived therefrom.

Amino crosslinker resins (e.g., aminoplasts) are typically thecondensation products of aldehydes (e.g., such as formaldehyde,acetaldehyde, crotonaldehyde, and benzaldehyde) with amino- oramido-group-containing substances (e.g., urea, melamine andbenzoguanamine). Suitable amino crosslinking resins include, forexample, benzoguanamine-formaldehyde-based resins,melamine-formaldehyde-based resins (e.g., hexamethonymethyl melamine),etherified melamine-formaldehyde, urea-formaldehyde-based resins, andmixtures thereof.

Condensation products of other amines and amides can also be employedsuch as, for example, aldehyde condensates of triazines, diazines,triazoles, guanadines, guanamines and alkyl- and aryl-substitutedmelamines. Some examples of such compounds are N,N′-dimethyl urea,benzourea, dicyandimide, formaguanamine, acetoguanamine, glycoluril,ammelin 2-chloro-4,6-diamino-1,3,5-triazine,6-methyl-2,4-diamino-1,3,5-triazine, 3,5-diaminotriazole,triaminopyrimidine, 2-mercapto-4,6-diaminopyrimidine,3,4,6-tris(ethylamino)-1,3,5-triazine, and the like. While the aldehydeemployed is typically formaldehyde, other similar condensation productscan be made from other aldehydes, such as acetaldehyde, crotonaldehyde,acrolein, benzaldehyde, furfural, glyoxal and the like, and mixturesthereof.

Suitable commercially available amino crosslinking resins include, forexample, CYMEL 301, CYMEL 303, CYMEL 370, CYMEL 373, CYMEL 1125, CYMEL1131, CYMEL 5010 and MAPRENAL MF 980 (all available from CytecIndustries Inc., West Patterson, N.J.), and URAMEX BF 892 (availablefrom DSM, Netherlands).

Non-limiting examples of blocked isocyanate crosslinkers includealiphatic and/or cycloaliphatic blocked polyisocyanates such as HDI(hexamethylene diisocyanate), IPDI (isophorone diisocyanate), TMXDI(bis[4-isocyanatocyclohexyl]methane), H₁₂MDI (tetramethylene-m-xylidenediisocyanate), TMI (isopropenyldimethyl-benzylisocyanate) and dimers ortrimers thereof. Suitable blocking agents include, for example,n-butanone oxime, ε-caprolactam, diethyl malonate, and secondary amines.Non-limiting examples of suitable commercially available blockedisocyanate crosslinkers include VESTANAT B 1358 A, VESTANAT EP B 1186 A,VESTANA EP B 1299 SV (all available from Degussa Corp., Marl, Germany);and DESMODUR VPLS 2078 and DESMODURBL 3175 (available from Bayer A. G.,Leverkusen, Germany). In some embodiments, blocked isocyanates may beused that have an Mn of at least about 300, more preferably at leastabout 650, and even more preferably at least about 1,000.

Certain conventional polyester coatings are crosslinked using reactivediluents such as, for example, styrene. Preferred coating compositionsof the invention are free, or at least substantially free, of suchreactive diluent crosslinker, which may be unsuitable for food-contactapplications. Preferred crosslinkers have an Mn of at least about 500.

One preferred optional ingredient is a catalyst to increase the rate ofcure and/or the extent of crosslinking Non-limiting examples ofcatalysts, include, but are not limited to, strong acids (e.g.,dodecylbenzene sulphonic acid (DDBSA), available as CYCAT 600 fromCytec, methane sulfonic acid (MSA), p-toluene sulfonic acid (pTSA),dinonylnaphthalene disulfonic acid (DNNDSA), and triflic acid),quaternary ammonium compounds, phosphorous compounds, tin and zinccompounds, and combinations thereof. Specific examples include, but arenot limited to, a tetraalkyl ammonium halide, a tetraalkyl or tetraarylphosphonium iodide or acetate, tin octoate, zinc octoate,triphenylphosphine, and similar catalysts known to persons skilled inthe art. If used, a catalyst is preferably present in an amount of atleast 0.01 wt-%, and more preferably at least 0.1 wt-%, based on theweight of nonvolatile material in the coating composition. If used, acatalyst is preferably present in an amount of no greater than 3 wt-%,and more preferably no greater than 1 wt-%, based on the weight ofnonvolatile material in the coating composition.

In some embodiments, the UC-functional polymer of the invention mayself-crosslink when cured under suitable coating cure conditions. Anefficacious amount of one or more metal driers may be included in thecoating composition (with or without crosslinker) to facilitate theformation of crosslinks between the UC-groups. Non-limiting examples ofsuitable metal driers may include aluminum (Al), antimony (Sb), barium(Ba), bismuth (Bi), calcium (Ca), cerium (Ce), chromium (Cr), cobalt(Co), copper (Cu), iridium (Ir), iron (Fe), lead (Pb), lanthanum (La),lithium (Li), manganese (Mn), Neodymium (Nd), nickel (Ni), rhodium (Rh),ruthenium (Ru), palladium (Pd), potassium (K), osmium (Os), platinum(Pt), sodium (Na), strontium (Sr), tin (Sn), titanium (Ti), vanadium(V), Yttrium (Y), zinc (Zn), zirconium (Zr), or any other suitable rareearth metal or transition metal, as well as oxides, salts (e.g., acidsalts such as octoates, naphthenates, stearates, neodecanoates, etc.) orcomplexes of any of these, and mixtures thereof.

If desired, coating compositions of the invention may optionally includeother additives that do not adversely affect the coating composition ora cured coating resulting therefrom. The optional additives arepreferably at least substantially free of mobile and/or bound BPA andaromatic glycidyl ether compounds (e.g., BADGE, BFDGE and epoxy novalaccompounds) and are more preferably completely free of such compounds.Suitable additives include, for example, those that improve theprocessability or manufacturability of the composition, enhancecomposition aesthetics, or improve a particular functional property orcharacteristic of the coating composition or the cured compositionresulting therefrom, such as adhesion to a substrate. Additives that maybe included are carriers, additional polymers, emulsifiers, pigments,metal powders or paste, fillers, anti-migration aids, anti-microbials,extenders, curing agents, lubricants, coalescents, wetting agents,biocides, plasticizers, crosslinking agents, antifoaming agents,colorants, waxes, anti-oxidants, anticorrosion agents, flow controlagents, thixotropic agents, dispersants, adhesion promoters, UVstabilizers, scavenger agents or combinations thereof. Each optionalingredient can be included in a sufficient amount to serve its intendedpurpose, but preferably not in such an amount to adversely affect acoating composition or a cured coating resulting therefrom.

Any suitable carrier may be used to prepare coating compositions of theinvention. Suitable carriers include carrier liquids such as organicsolvents, water, and mixtures thereof. Preferably, the liquid carrier(s)are selected to provide a dispersion or solution of the UC-functionalpolymer of the invention for further formulation. Suitable organicsolvents include aliphatic hydrocarbons (e.g., mineral spirits,kerosene, high flashpoint VM&P naphtha, and the like); aromatichydrocarbons (e.g., benzene, toluene, xylene, solvent naphtha 100, 150,200 and the like); alcohols (e.g., ethanol, n-propanol, isopropanol,n-butanol, iso-butanol and the like); ketones (e.g., acetone,2-butanone, cyclohexanone, methyl aryl ketones, ethyl aryl ketones,methyl isoamyl ketones, and the like); esters (e.g., ethyl acetate,butyl acetate and the like); glycols (e.g., butyl glycol); glycol ethers(e.g., ethylene glycol monomethyl ether, ethylene glycol monoethylether, ethylene glycol monobutyl ether, propylene glycol monomethylether, methoxypropanol and the like); glycol esters (e.g., butyl glycolacetate, methoxypropyl acetate and the like); and mixtures thereof.

If present, the amount of liquid carrier included in the coatingcomposition will vary, for example, depending upon the applicationmethod and the desired amount of solids. Preferred embodiments of thecoating composition include at least 30 wt-% of liquid carrier, moretypically at least 45 wt-% of liquid carrier. In such embodiments, thecoating composition will typically include less than 85 wt-% of liquidcarrier, more typically less 80 wt-% of liquid carrier.

In some embodiments, the coating composition is a solvent-based coatingcomposition that preferably includes no more than a de minimus amount(e.g., 0 to 2 wt-%) of water. In other embodiments, the coatingcomposition can include a substantial amount of water.

In some embodiments, the coating composition of the invention is awater-based varnish. As already discussed, the UC-functional polymer ofthe invention may include water-dispersing groups such as salt groups.In some embodiments, preferably at least about 50 wt-% of the liquidcarrier system is water, more preferably at least about 60 wt-% iswater, and even more preferably at least about 75 wt-% is water. Certaincoating compositions of the invention include at least about 10 wt-% ofwater, more preferably at least about 20 wt-% of water, and even morepreferably at least about 40 wt-% of water (in some embodiments about 50wt-% or more of water), based on the total weight of the coatingcomposition.

Coating compositions of the invention may be prepared by conventionalmethods in various ways. For example, the coating compositions may beprepared by simply admixing the UC-functional polymer, optionalcrosslinker and any other optional ingredients, in any desired order,with sufficient agitation. The resulting mixture may be admixed untilall the composition ingredients are substantially homogeneously blended.Alternatively, the coating compositions may be prepared as a liquidsolution or dispersion by admixing an optional carrier liquid, theUC-functional polymer, optional crosslinker, and any other optionalingredients, in any desired order, with sufficient agitation. Anadditional amount of carrier liquid may be added to the coatingcompositions to adjust the amount of nonvolatile material in the coatingcomposition to a desired level.

The total amount of solids present in coating compositions of theinvention may vary depending upon a variety of factors including, forexample, the desired method of application. Presently preferred coatingcompositions include at least about 30, more preferably at least about35, and even more preferably at least about 40 wt-% of solids, based onthe total weight of the coating composition. In certain preferredembodiments, the coating composition includes less than about 80, morepreferably less than about 70, and even more preferably less than about65 wt-% of solids, based on the total weight of the coating composition.The solids of the coating composition may be outside the above rangesfor certain types of applications. For example, for inside sprayapplications of the coatings compositions, the wt-% solids may be as lowas about 20 wt-%.

Cured coatings of the invention preferably adhere well to metal (e.g.,steel, tin-free steel (TFS), tin plate, electrolytic tin plate (ETP),aluminum, etc.) and provide high levels of resistance to corrosion ordegradation that may be caused by prolonged exposure to products such asfood or beverage products. The coatings may be applied to any suitablesurface, including inside surfaces of containers, outside surfaces ofcontainers, container ends, and combinations thereof.

The coating composition of the invention can be applied to a substrateusing any suitable procedure such as spray coating, roll coating, coilcoating, curtain coating, immersion coating, meniscus coating, kisscoating, blade coating, knife coating, dip coating, slot coating, slidecoating, and the like, as well as other types of premetered coating. Inone embodiment where the coating is used to coat metal sheets or coils,the coating can be applied by roll coating.

The coating composition can be applied on a substrate prior to, orafter, forming the substrate into an article. In some embodiments, atleast a portion of a planar substrate is coated with one or more layersof the coating composition of the invention, which is then cured beforethe substrate is formed into an article (e.g., via stamping, drawing, ordraw-redraw).

After applying the coating composition onto a substrate, the compositioncan be cured using a variety of processes, including, for example, ovenbaking by either conventional or convectional methods. The curingprocess may be performed in either discrete or combined steps. Forexample, the coated substrate can be dried at ambient temperature toleave the coating composition in a largely un-crosslinked state. Thecoated substrate can then be heated to fully cure the coatingcomposition. In certain instances, the coating composition can be driedand cured in one step. In preferred embodiments, the coating compositionof the invention is a heat-curable coating composition.

The curing process may be performed at any suitable temperature,including, for example, temperatures in the range of about 180° C. toabout 250° C. If metal coil is the substrate to be coated, curing of theapplied coating composition may be conducted, for example, by subjectingthe coated metal to an elevated temperature environment of about 210° C.to about 232° C. for a suitable time period (e.g., about 15 to 30seconds). If metal sheeting is the substrate to be coated (e.g., such asused to make three-piece food cans), curing of the applied coatingcomposition may be conducted, for example, by subjecting the coatedmetal to an elevated temperature environment of about 190° C. to about210° C. for a suitable time period (e.g., about 8 to about 12 minutes).

Coating compositions of the invention may be useful in a variety ofcoating applications. As previously discussed, the coating compositionsare particularly useful as adherent coatings on interior or exteriorsurfaces of metal packaging containers. Non-limiting examples of sucharticles include closures (including, e.g., internal surfaces oftwist-off caps for food and beverage containers); internal crowns; twoand three-piece cans (including, e.g., food and beverage containers);shallow drawn cans; deep drawn cans (including, e.g., multi-stage drawand redraw food cans); can ends (including, e.g., easy open can ends);monobloc aerosol containers; and general industrial containers, cans,and can ends.

Preferred coating compositions of the invention are particularly suitedfor use on interior or exterior surfaces of metal food or beveragecontainers, including as food-contact coatings. Preferably, the curedcoatings are retortable when employed in food and beverage containerapplications. Preferred cured coatings of the invention are capable ofwithstanding elevated temperature conditions frequently associated withretort processes or other food or beverage preservation or sterilizationprocesses. Particularly preferred cured coatings exhibit enhancedresistance to such conditions while in contact with food or beverageproducts that exhibit one or more aggressive (or corrosive) chemicalproperties under such conditions. Some examples of such aggressive foodor beverage products may include meat-based products, milk-basedproducts, fruit-based products, energy drinks, and acidic or acidifiedproducts.

The coating composition of the invention is particularly suitable foruse as a coating on an interior surface of the sidewall of a three-piecefood can. The coating composition is typically applied to a metal sheetwhich is then typically cured prior to fabricating the coated sheet intothe sidewall of a three-piece food can.

Some additional non-limiting embodiments of the invention are providedbelow.

-   -   A. A composition comprising: a polymer (i) having a backbone or        pendant UC group with a double bond, more preferably a        carbon-carbon double bond, located between atoms of a ring,        and (ii) preferably having an iodine value of at least about 10,        more preferably at least about 20, even more preferably at least        about 35, and optimally at least about 50; and an optional        crosslinker.    -   B. An article, comprising: a metal substrate having the        composition of Embodiment A applied on at least a portion of a        major surface of the metal substrate.    -   C. A method comprising: providing the composition of Embodiment        A, and applying the composition on at least a portion of a metal        substrate.    -   D. Any of Embodiments A-C, wherein the one or more UC groups        constitute at least about 5 wt-% of the polymer, more preferably        at least about 15 wt-%, and even more preferably at least 30        wt-%, based on the total weight of UC-functional monomers        included in the polymer relative to the total weight of the        polymer.    -   E. Any of Embodiments A-D, wherein the UC group comprises an        unsaturated group that is at least bicyclic (e.g., bicyclic,        tricylic, or higher order polycyclic group), and more preferably        bicyclic.    -   F. The composition, article, or method of Embodiment E, wherein        the bicyclic group comprises a structure represented by the        nomenclature expression bicyclo[x.y.z]alkene, wherein: x is 2 or        more, and y and z are each at least 1.    -   G. The composition, article, or method of Embodiment E, wherein        the unsaturated bicyclic group comprises bicyclo[2.1.1]hexene,        bicyclo[2.2.1]heptene, bicyclo[2.2.1]heptadiene,        bicyclo[2.2.2]octene, bicyclo[2.2.2]octadiene, or a mixture        thereof    -   H. Any of Embodiments A-G, wherein the UC group is provided by        nadic acid, nadic anhydride, methyl-nadic acid, methyl-nadic        anhydride, a derivative thereof, or a mixture thereof    -   I. Any of Embodiments A-E, wherein the UC group comprises an        unsaturated strained ring group.    -   J. Any of Embodiments A-I, wherein the UC group includes at        least one allylic hydrogen.    -   K. Any of Embodiments A-J, wherein the polymer has a polymer        backbone that includes at least one heteroatom and, more        preferably, the backbone comprises a step-growth or condensation        backbone.    -   L. Any of Embodiments A-K, wherein the backbone of the polymer        comprises a polyester backbone, a polyether backbone, a        polyurethane backbone, or a copolymer backbone thereof (e.g., a        polyester-urethane backbone, a polyester-ether backbone, etc.).    -   M. Any of Embodiments A-L, wherein the crosslinker comprises an        amino crosslinker, an anhydride-based crosslinker, a blocked        isocyanate crosslinker, a phenolic crosslinker, an        epoxy-functional crosslinker or a mixture thereof.    -   N. Any of Embodiments A-M, wherein the composition includes at        least 5 wt-%, more preferably at least 10 wt-%, and even more        preferably at least 15 wt-%, by total weight solids, of the        crosslinker.    -   O. Any of Embodiments A-N, wherein the composition includes at        least 50% by weight of binder polymer, and more preferably at        least 60 wt-% or at least 70 wt-%.    -   P. Any of Embodiments A-O, wherein the crosslinker comprises a        phenolic crosslinker, more preferably a resole phenolic        crosslinker.    -   Q. Any of Embodiments A-P, wherein the composition further        comprises a liquid carrier.    -   R. Any of Embodiments A-Q, wherein the composition comprises a        cured coating composition, more preferably a crosslinked coating        composition.    -   S. The composition, article, or method of Embodiment R, wherein        the crosslinker comprises a phenolic crosslinker, more        preferably a resole phenolic crosslinker, which is covalently        attached to the polymer through a linkage resulting from the        reaction of the UC group and the phenolic crosslinker.    -   T. Any of Embodiments B-S, wherein the metal substrate comprises        a substrate of a metal food or beverage can or portion thereof    -   U. Any of Embodiments A-T, wherein the polymer comprises a        water-dispersible polymer, more preferably a water-dispersible        polymer having a sufficient number of salt groups to form a        stable aqueous solution or dispersion.    -   V. Any of Embodiments A-T, wherein the composition comprises a        solvent-based composition.    -   W. Any of Embodiments A-V, wherein the polymer comprises a        polyester binder polymer (preferably present in the coating        composition, based on total coating solids, in an amount from        50-95 wt-%) and the crosslinker comprises a phenolic        crosslinker, more preferably a resole phenolic crosslinker.

Test Methods

Unless indicated otherwise, the following test methods were utilized inthe Examples that follow.

A. Solvent Resistance Test

The extent of “cure” or crosslinking of a coating is measured as aresistance to solvents, such as methyl ethyl ketone (MEK) or isopropylalcohol (IPA). This test is performed as described in ASTM D5402-93. Thenumber of double-rubs (i.e., one back-and-forth motion) is reported.Preferably, the MEK solvent resistance is at least 30 double rubs.

B. Adhesion Test

Adhesion testing was performed to assess whether the coatingcompositions adhere to the coated substrate. The Adhesion Test wasperformed according to ASTM D3359-Test Method B, using SCOTCH 610 tape,available from 3M Company of Saint Paul, Minn. Adhesion is generallyrated on a scale of 0-10 where a rating of “10” indicates no adhesionfailure, a rating of “9” indicates 90% of the coating remains adhered, arating of “8” indicates 80% of the coating remains adhered, and so on. Acoating is considered herein to satisfy the Adhesion Test if it exhibitsan adhesion rating of at least 8.

C. Blush Resistance Test

Blush resistance measures the ability of a coating to resist attack byvarious solutions. Typically, blush is measured by the amount of waterabsorbed into a coated film. When the film absorbs water, it generallybecomes cloudy or looks white. Blush was measured visually using a scaleof 0-10 where a rating of “10” indicates no blush, a rating of “5”indicates slight whitening of the film, and a rating of “0” indicatessevere whitening of the film.

D. Water Pasteurization (Also Referred to as Water Retort)

Water retort is a measure of the coating integrity of the coatedsubstrate after exposure to heat and pressure with a liquid such aswater. Water retort performance is not necessarily required for all foodand beverage coatings, but is desirable for some product types that arepacked under retort conditions. Testing is accomplished by subjectingthe substrate to heat ranging from 105-130° C. and pressure of 15 psi(˜1.05 kg/cm²) for a period of 15 to 90 minutes. The coated substratewas then tested for adhesion and blush as described above.

E. Iodine Value

Prepare Starch Solution by dissolving 5 grams of soluble starch with 100milliliters (ml) of deionized (D.I.) water. Add 400 ml of boiling D.I.water, stir until clear, and allow to cool. This solution will not keepfor more than a few days and should be made fresh as needed. PreparePotassium Iodide Solution by dissolving 150 grams of Potassium Iodide in1,000 ml of D.I. water.

A small portion of the sample under test shall be weighed by differenceinto an Erlenmeyer iodine flask, the amount of sample taken being suchthat from 10 to 30% of an iodine solution (Wijs Iodine MonochlorideSolution—Fisher Scientific Co. Cat. No. SI106-4) will be absorbed.Pipette 20 ml of chloroform into each sample flask. Stopper the flasks,add a Teflon stirring bar and stir until the samples dissolve. Preparetwo flasks for blanks by pipetting 20 ml of chloroform into separateflasks. Pipette into each flask (2 flasks for each sample and 2 flasksfor blanks) 25 ml of the iodine solution.

Stopper the flasks, stir for 30 seconds, then let stand with occasionalswirling for 30 minutes in a dark place at room temperature. At the endof the standing time, pipette 20 ml. of Potassium Iodide Solution and 80ml of D.I. water, stopper and stir. Add 2 ml of the Starch Solution andimmediately titrate with 0.1N sodium thiosulfate (Fisher Scientific Cat.No. SS368-1).

Calculate the iodine value as the difference in the average volume (inmilliliters) of 0.1N sodium thiosulfate required for the blank less theaverage volume (in milliliters) required for the sample, multiplied by1.269 and divided by the sample weight in grams.

The iodine value is calculated using the following equation: [(Averagevolume blank−Average volume sample)×1.269]/[Sample Weight in grams]. Theiodine value is reported as the centigrams of iodine absorbed per 1 gramof the material.

The iodine values provided in the Examples Section were determined usingthis methodology.

EXAMPLES

The invention is illustrated by the following examples. It is to beunderstood that the particular examples, materials, amounts, andprocedures are to be interpreted broadly in accordance with the scopeand spirit of the inventions as set forth herein. Unless otherwiseindicated, all parts and percentages are by weight and all molecularweights are weight average molecular weight. Unless otherwise specified,all chemicals used are commercially available from, for example,Sigma-Aldrich, St. Louis, Mo.

Example 1 UC-Functional Polyesters Run 1: Polyester Containing NadicAnhydride

Cyclohexane-1,4-dimethanol (124.1 g of a 90% solution in water),2-methyl-1,3-propanediol (64.6 g), terephthalic acid (42.3 g),isophthalic acid (84.4 g), and dibutyltin oxide (0.40 g) were charged toa 1-liter, 4-neck round bottom flask fitted with a mechanical stirrer, athermocouple, a packed column (topped with a Dean-Stark trap andcondenser), and a stopper for future additions. The contents of theflask were heated slowly (so that the temperature of the distillate didnot exceed 100° C.) to 230° C., and held until the acid number droppedto 0.4 mg KOH/g resin. The temperature was then reduced to 180° C., andcyclohexane-1,4-dicarboxylic acid (63.3 g) and nadic anhydride (50.2 g)were added to the flask. The temperature was raised to 220° C. and helduntil the resin cleared. The temperature was dropped to 180° C., xylene(19.5 g) was added to the flask, the packed column was removed, and thetrap was pre-filled with xylene in preparation for an azeotrope reflux.The temperature was then returned to 220° C. (or as restricted byreflux) and held until the acid number dropped below 5 mg KOH/g resin.At this point, the resin was cooled to 170° C. and cut to 50% solidswith AROMATIC 150 solvent (166.8 g) and cyclohexanone (166.8 g). Onceuniform, the resin was fully cooled and discharged.

Run 2: Polyester Containing Nadic Anhydride and Pyromellitic Dianhydride(PMDA)

Cyclohexane-1,4-dimethanol (626.2 g of a 90% solution in water),2-methyl-1,3-propanediol (325.8 g), terephthalic acid (158.1 g),isophthalic acid (315.8 g), and dibutyltin oxide (1.9 g) were charged toa 5-liter, 4-neck round bottom flask fitted with a mechanical stirrer, athermocouple, a packed column (topped with a Dean-Stark trap andcondenser), and a stopper for future additions. The contents of theflask were heated slowly (so that the temperature of the distillate didnot exceed 100° C.) to 232° C. under a nitrogen atmosphere, and helduntil the acid number dropped to 1.0 mg KOH/g resin. The temperature wasthen reduced to 170° C., and nadic anhydride (585.0 g) was added to theflask. Following a 1-hour hold at 170° C., xylene (154.9 g) was added tothe flask, the packed column was removed, and the trap was pre-filledwith xylene in preparation for an azeotrope reflux. The temperature wasthen raised to 220° C. (or as restricted by reflux) and held until theacid number dropped below 2 mg KOH/g resin. At this point, the resin wascooled to 170° C. and cut to 60% solids with cyclohexanone (1032.5 g).The resulting resin was stirred until uniform and 2697.0 grams weretransferred to a 5-liter flask fitted with a mechanical stirrer, athermocouple, a condenser, and a stopper for sampling or additions.Pyromellitic dianhydride (86.9 g) was added to the flask, and thecontents were heated to 120° C. under a nitrogen atmosphere. After a4-hour hold at 120° C., cyclohexanone (222.0 g) and AROMATIC 150 solvent(1149.0 g) were added to achieve a 41% solids solution, and the resinwas cooled to room temperature. The resulting resin had an acid numberof 30.2 mg KOH/g resin, a hydroxyl number of 26.4 mg KOH/g resin, and aTg of 68° C.

Run 3: Water-Based Polyester Containing Nadic Anhydride and PMDA

Cyclohexane-1,4-dimethanol (1284.4 g of a 90% solution in water),2-methyl-1,3-propanediol (668.0 g), terephthalic acid (324.0 g),isophthalic acid (648.0 g), and dibutyltin oxide (2.5 g) were charged toa 5-liter, 4-neck round bottom flask fitted with a mechanical stirrer, athermocouple, a packed column (topped with a Dean-Stark trap andcondenser), and a stopper for future additions. The contents of theflask were heated slowly (so that the temperature of the distillate didnot exceed 100° C.) to 232° C. under a nitrogen atmosphere, and helduntil the acid number dropped to 0.6 mg KOH/g resin. The temperature wasthen reduced to 170° C., and nadic anhydride (1200.0 g) was added to theflask. Following a 1-hour hold at 170° C., xylene (254.0 g) was added tothe flask, the packed column was removed, and the trap was pre-filledwith xylene in preparation for an azeotrope reflux. The temperature wasthen raised to 220° C. (or as restricted by reflux) and held until theacid number dropped below 2 mg KOH/g resin. At this point, the resin wascooled to 170° C. and cut to 81% solids with cyclohexanone (659.0 g).The resulting resin was stirred until uniform and 2175.0 grams weretransferred to a 5-liter flask fitted with a mechanical stirrer, athermocouple, a condenser, and a stopper for sampling or additions.Pyromellitic dianhydride (117.6 g) was added to the flask, and thecontents were heated to 120° C. under a nitrogen atmosphere. After a4-hour hold at 120° C., butanol (405.0 g) and butyl cellosolve (405.0 g)were added to achieve a 58% solids solution, and the resin was cooled toroom temperature. The resulting resin had an acid number of 23.6 mgKOH/g resin. 384.9 grams of the resulting solution were combined withdimethylethanolamine (6.7 g) and heated to 60° C. in a 1-liter roundbottom flask under mechanical stirring. D.I. water (248.4 g) was addedto the flask over 30 minutes (resulting in a 35% solids) while thetemperature of the batch was allowed to cool to room temperature.

Run 4: Polyester Containing Unsaturated at Least Bicyclic Groups FormedVia Diels-Alder Reaction)

Cyclohexane-1,4-dimethanol (267.7 g of a 90% solution in water),2-methyl-1,3-propanediol (101.0 g), terephthalic acid (60.8 g),isophthalic acid (121.5 g), and dibutyltin oxide (0.82 g) were chargedto a 2-liter, 4-neck round bottom flask fitted with a mechanicalstirrer, a thermocouple, a packed column (topped with a Dean-Stark trapand condenser), and a stopper for future additions. The contents of theflask were heated slowly (so that the temperature of the distillate didnot exceed 100° C. at the top of packed column) to a batch temperatureof 235° C. under a nitrogen atmosphere. The temperature was held at 235°C. until the acid number dropped to 0.5 mg KOH/g resin. The temperaturewas then reduced to 160° C., and maleic anhydride (134.5 g) and xylene(66.2 g) were added to the flask. The packed column was removed, andthen the Dean-Stark trap was fitted directly to the flask and pre-filledwith xylene in preparation for an azeotrope reflux. The temperature wasreturned to approximately 200° C. and held until the acid number droppedbelow 3 mg KOH/g resin. At this point, the resin was cooled to 160° C.,and dicyclopentadiene (95.5 g, 95% pure) was added slowly to the flaskover 1 hour. The resin was held for 5 hours at 160° C., and then 200.0 gof AROMATIC 150 was added slowly. The resin was returned to reflux, andany distillate was collected in the Dean-Stark trap. Once thetemperature of the distillate reached 180° C., the resin was cooled to180° C. and an additional 220.0 g of AROMATIC 150 was added slowly tothe flask. Upon further cooling to 120° C., Pyromellitic dianhydride(37.2 g) was added to the flask and the contents stirred for four hoursat 120° C. Cyclohexanone (398.0 g) was added slowly, and the resin wascooled to room temperature. The resulting resin had an acid number of27.4 mg KOH/g resin, a hydroxyl number of 17.6 mg KOH/g resin, and aGardner-Holt viscosity of Z1 at 44.5% solids.

Example 2 Coating Compositions Run 1

A solvent-based coating composition was prepared that included, based ontotal coatings solids, 75 wt-% of the polyester resin of Example 1, Run1 and 25 wt-% of GPRI 7590 resole phenolic crosslinker(Georgia-Pacific). The coating composition was approximately 40 wt-%solids.

Run 2

A solvent-based coating composition was prepared that included, based ontotal coatings solids, 75 wt-% of the polyester resin of Example 1, Run2 and 25 wt-% of GPRI 7590 resole phenolic crosslinker(Georgia-Pacific). The coating composition was approximately 40 wt-%solids.

Comparative Run 3

A commercial solvent-based, epoxy-based coating composition including aphenolic crosslinker was provided as a control.

Example 3 Cured Coating Compositions

The coating compositions of Example 2 were applied to metal substrateand cured to form cured coatings. The results of coating performancetests performed on the cured coatings are provided below in Tables 1 and2.

TABLE 1 Retort and Fabrication Properties Example 2, Comparative Example2, Example 2, Coating Composition Run 3 Run 1 Run 2 Adhesion 10 10 10MEK Resistance (double 35 >100  >100  rubs) Water Retort¹ Blush (L/V)10/10 10/10 10/10 Adhesion (L/V) 10/10 10/10 10/10 Size 202 Sanitary CanEnd Crazing None None None Metal Exposure (milli-Amps)²   6.4   2.8  7.4 CuSO₄ Corrosion³ None None None Size 206 Sanitary Can End CrazingNone None None Metal Exposure (ma)²   11.2   6.2   13.5 CuSO₄ Corrosion³None None None Bake: 10 minutes at a 400° F. (204° C.) peak metaltemperature (PMT) in a gas-fired forced-draft box oven Substrate: 0.2575# ETP Coating Wt: 4.5-5.0 msi (milligrams per square inch); metricequivalent is 7-7.8 grams per square meter Rating Scale: 0-10; 10 = NoFailure ¹60 minutes at 250° F. (121° C.) and 15 psi (~1.05 kg/cm²) indistilled water pursuant to Test Method D; L/V = Liquid/Vapor phase²Electrolyte-1% NaCl; Average of 4 ends ³Ends submersed for 10 minutesin CuSO₄/HCl solution.

TABLE 2 Corrosion Resistance ETP TFS Example 2, Example 2, ComparativeExample 2, Example 2, Comparative Example 2, Example 2, Run 3 Run 1 Run2 Run 3 Run 1 Run 2 2% Salt/3% Acetic Acid Solution Adhesion/Blush 10/1010/9   9/10 8/5  8/8  8/7  Corrosion 9 9 9 4 5 6 1% Lactic Acid SolutionAdhesion/Blush 9/8  9/10  9/10 7/4  8/9  7/10 Corrosion 8 8 9 4 5 7 2%Salt Solution Adhesion/Blush  5/10 10/10 5/7 6/10 9/10 4/8  Corrosion 910 9 9 10 9 Testing conducted using size 202 sanitary can ends; Endssubmersed in specified solution and retorted 60 minutes at 250° F. (121°C.) and 15 psi (~1.05 kg/cm²). Bake: 10 minutes at a 400° F. (204° C.)PMT in a gas-fired forced-draft box oven Substrates: 0.25 75# ETP and75# TFS Coating Wt.: 4.5-5.0 msi (milligrams per square inch); metricequivalent is 7-7.8 grams per square meter Rating Scale: 0-10; 10 = NoFailure

Example 4 UC-Functional Polyurethane

Cyclohexane dimethanol (1449.7 g of a 90% solution in water), MP Diol(i.e., methylpropanediol) (722.5 g), terephthalic acid (293.3 g),isophthalic acid (578 g), maleic anhydride (808.4 g), dibutyl tin oxide(4.2 g) (FASTCAT 4201 product), and xylene (187 g) were added to a glassreaction flask equipped with a stirrer, nitrogen inlet and refluxcondenser. The condenser was further equipped with a Dean-Stark flask tocapture and quantify the water evolved during the reaction. The reactorwas set for 230° C. After approximately 5 hours, the acid value of theresulting polyester polymer was approximately 0.5 mg KOH/g resin. Thetemperature of the reactor was reduced to approximately 160° C., atwhich point dicyclopentadiene (“DCPD”) (546.4 g) was added. The reactorwas held an additional 6 hours at 160° C. to complete the Diels-Alderreaction between the maleic unsaturation and the DCPD. The resultingstructure is believed to resemble that of a material prepared from nadicanhydride. The resulting modified polyester polymer composition was 84%solids and had an acid value of 1.4 mg KOH/g resin and an OH value of56.6 mg KOH/g resin.

The modified polyester composition (1044.3 g) was added to a newreaction flask (same configuration as described above), along withisophorone diisocyanate (“IPDI”) (247.3 g) and dimethylol propionic acid(74.6 g). The temperature of the flask was maintained at about 100° C.and the reaction was continued for about 6 hours, at which point butanol(307 g), butyl cellosolve (307 g), and cyclohexanone (1587 g) were addedto the flask. The resulting polyester-urethane polymer composition was24% solids and had an acid value of 26.5 mg KOH/g resin.

Example 5 Coating Composition

The polyester-urethane polymer composition of Example 4 (100 g) wascombined with a resole phenolic crosslinker resin (7.5 g). The resultingcoating formulation had a ratio, on a weight basis, of 80%polyester-urethane polymer and 20% phenolic resin.

Example 6 Cured Coating Composition

A sample of the Example 5 coating composition was applied onto bothcommercially available ETP and tin-free steel TFS using a wound wirerod. The coated steel samples were baked about 12 minutes in a 402° F.(204° C.) oven to dry and cure the coating. Once dried and cured, thefilm weight of the coating was determined to be from about 4.5 to 5.0mgs coating per square inch of coated substrate (metric equivalent is7-7.8 grams per square meter). It was noted that the appearance of thecoating was smooth and glossy and had a goldish tint. Samples of thiscoated substrate were fabricated into food can ends, with the coatingcomposition of Example 5 oriented as the internal coating. In addition,an analogous set of control food can ends were prepared from tin-platedand tin-free steel coated with a conventional epoxy-based coating systemthat is currently used commercially as a high corrosion-resistantcoating for the interior of food can bodies and ends. Samples of boththe control and experimental ends were then subjected to a variety ofcoating property tests to evaluate the suitability of the coatings foruse as food-contact coatings for food or beverage cans. The curedcoating composition of Example 6 on ETP substrate exhibited good coatingproperties (e.g., comparable adhesion, blush resistance, stainresistance, and corrosion resistance as that of the commercial control).The cured coating composition of Example 6 on TFS substrate alsoexhibited good coating properties, although not quite as good as on ETPsubstrate (e.g., the adhesion and corrosion resistance were not asgood).

The entire contents of copending application entitled POLYESTER COATINGCOMPOSITION by Hayes et al., filed on even date herewith, isincorporated by reference.

The complete disclosure of all patents, patent applications, andpublications, and electronically available material cited herein areincorporated by reference. The foregoing detailed description andexamples have been given for clarity of understanding only. Nounnecessary limitations are to be understood therefrom. The invention isnot limited to the exact details shown and described, for variationsobvious to one skilled in the art will be included within the inventiondefined by the claims.

What is claimed is: 1-20. (canceled)
 21. An article comprising: a metalsubstrate of a food or beverage container or a portion thereof; and acoating applied on at least a portion of a surface of the metalsubstrate, wherein the coating is formed from a coating compositioncomprising a polyester polymer having a backbone or pendant unsaturatedmonocyclic cycloaliphatic group.
 22. The article of claim 21, whereinthe unsaturated monocyclic cycloaliphatic group includes a substitutedor unsubstitituted C3-C13 ring.
 23. The article of claim 21, wherein theunsaturated monocyclic cycloaliphatic group includes a substituted orunsubstitituted C4-C9 ring.
 24. The article of claim 21, wherein theunsaturated monocyclic cycloaliphatic group comprises a substituted orunsubstituted: cyclobutene, cyclopentene, cyclopentadiene, cyclohexene,cyclohexadiene, cycloheptene, cycloheptadiene, cyclooctene,cyclooctadiene, cyclononene, cyclodecene, cyclodecadiene, cycloundecene,cyclododecenes, cyclotridecene, or cyclononadiene.
 25. The article ofclaim 21, wherein the unsaturated monocyclic cycloaliphatic groupcomprises a substituted or unsubstituted group selected fromcyclopropene, cyclobutene, trans-cyclooctene, trans-cyclononene,cyclobutadiene, cyclopentadiene, 1,3-cyclohexadiene,1,3-cycloheptadiene, 1,3 cyclooctadiene, 1,3 cyclononadiene, or1,3-cyclodecadiene.
 26. The article of claim 21, wherein the unsaturatedmonocyclic cycloaliphatic group has a ring that includes 3 to 5 atoms.27. The article of claim 21, wherein the unsaturated monocycliccycloaliphatic group has a ring that includes 3 to 4 atoms.
 28. Thearticle of claim 21, wherein the unsaturated monocyclic cycloaliphaticgroup has at least one double bond with a heat of hydrogenation greaterthan that of cyclohexene.
 29. The article of claim 21, wherein theunsaturated monocyclic cycloaliphatic group has at least one double bondwith a heat of hydrogenation at least about as high as that ofbicyclo[2.2.2]octene.
 30. The article of claim 21, wherein theunsaturated monocyclic cycloaliphatic group includes at least onecarbon-carbon bond located between atoms of a ring.
 31. The article ofclaim 21, wherein the polyester polymer includes a plurality of backboneunsaturated monocyclic cycloaliphatic groups.
 32. The article of claim21, wherein the polyester polymer has an iodine value of at least about10.
 33. The article of claim 21, wherein the polyester polymer has a Tgof at least 20° C.
 34. The article of claim 21, wherein the polyesterpolymer includes less than 3 weight percent of fatty acids and oils,based on the total non-volatile weight of ingredients used to make thepolyester polymer.
 35. The article of claim 21, wherein the polyesterpolymer includes less than 1 weight percent of long-chain hydrocarbonsincluding eight or more carbon atoms, based on the total non-volatileweight of ingredient used to make the polyester polymer.
 36. The articleof claim 21, wherein unsaturated monocyclic cycloaliphatic groupsconstitute at least about 5 weight percent of the polyester polymer. 37.The article of claim 21, wherein the polyester polymer is an aromaticpolyester polymer that includes at least 20 weight percent of aromaticgroups.
 38. The article of claim 21, wherein the polyester polymerincludes one or more step-growth linkages other than ester linkages. 39.The article of claim 21, wherein the unsaturated monocycliccycloaliphatic group includes at least one allylic hydrogen.
 40. Anarticle comprising: a metal substrate of a food or beverage can or aportion thereof; and a coating applied on at least a portion of aninterior surface of the metal substrate, wherein the coating is formedfrom a coating composition comprising a liquid carrier and an aromaticpolyester polymer having a backbone unsaturated monocycliccycloaliphatic group, wherein the polyester polymer has a Tg of at least0° C. and optionally includes one or more step-growth linkages otherthan ester linkages.